1. Field of the Invention
The present invention relates to a process for producing a monoalkenyl aromatic hydrocarbon compound. More particularly, the present invention relates to a process for producing a monoalkenyl aromatic hydrocarbon compound by alkenylating a side chain of an aromatic hydrocarbon compound by using a conjugated diene having 4 or 5 carbon atoms.
Monoalkenyl aromatic hydrocarbon compounds, such as monoalkenylbenzenes, are useful as intermediate materials for various organic compounds, such as monomers of macromolecular compounds, drugs, and the like. For example, 5-(o-tolyl)-2-pentene produced from o-xylene and 1,3-butadiene can be converted into industrially useful 2,6-naphthalenedicarboxylic acid by the successive ring closure, dehydrogenation, isomerization, and oxidation.
2. Description of the Related Arts
For producing a monoalkenylbenzene by alkenylating a side chain of an aromatic hydrocarbon compound with a conjugated diene having 4 or 5 carbon atoms, a process using an alkali metal, such as sodium and potassium, or an alloy thereof, as the catalyst has been known.
For example, a process using sodium metal as the catalyst is described in German Patent No. 557514. A process using potassium metal as the catalyst is described in Japanese Patent Publication No. Showa 50(1975)-17973. Processes using a potassium/sodium alloy or a mixture of potassium and sodium metals are described in Japanese Patent Publication Nos. Showa 50(1975)-17975 and Showa 51(1976)-8930.
A process using a product obtained by heat treatment of an alkali meal and an alkali metal compound as the catalyst is also known. For example, processes using a mixture obtained by heat treatment of a potassium compound and sodium metal as the catalyst are described in Japanese Patent Application Laid-Open Nos. Showa 47(1972)-27929 and Showa 47(1972)-31935.
It has been discovered by the group including the present inventors that a product obtained by heat treatment of a supported potassium compound and sodium metal shows the activity in the side chain alkenylation (specifications of United States Patent No. 5,344,806, and European Patent No. 569742A).
Among the processes described above, wherein when sodium metal is solely used as the catalyst without any treatment does not show either sufficient activity or sufficient selectivity and cannot be practical for the industrial process. Potassium metal, a potassium/sodium alloy, or a mixture of potassium and sodium metals as the catalyst shows a high catalytic activity. However, the catalysts react violently with oxygen and water. Therefore, when the process is industrially conducted, the possibility of hazard such as fire and explosion is large and the process has many problems with respect to safety.
The process using a mixture obtained by heat treatment of an alkali metal and an alkali metal compound at a high temperature is characterized in that neither potassium metal nor a potassium alloy is used for the reaction. However, when the powder catalyst prepared is transferred to a reactor or the like, operation problems, such as choking of the apparatus, tend to arise. Because the powder catalyst is a very reactive material, the operation having these problems is not preferable for the industrial embodiment from the standpoint of safety.
To overcome the problems described above, processes in which the catalyst is not transferred but the catalyst preparation and the production of an alkenylbenzene are conducted in the same reactor have been proposed in Japanese Patent Application Laid-Open Nos. Showa 47(1972)-27929 and Showa 47(1972)-31935. However, these processes show low process efficiencies in the industrial application and are not always practical.
When a small amount of water or oxygen is contained in the raw material, the catalyst is deactivated by the reaction with water or oxygen even when the amount of water or oxygen does not cause problems on the safety. Therefore, a large amount of the catalyst must be used to obtain a monoalkenylbenzene in a high yield.